ggplot(data = mpg, mapping = aes(x = displ, y = hwy)) +
geom_point(mapping = aes(colour = class)) +
geom_smooth(method = "lm") +
labs(
title = "Engine displacement and highway miles per gallon",
subtitle = "Values for seven different classes of cars",
x = "Engine displacement (L)",
y = "Highway miles per gallon"
)